Concerning the location of magnetopause merging as a function of the magnetopause current strength

Abstract

Abstract. We start from an assumption that merging occurs in regions of the magnetopause where current strengths are greater than some threshold value which corresponds to the total jump in the field across the magnetopause greater than 50 nT. Because time and cost constraints preclude running numerical simulations for a wide variety of interplanetary magnetic field (IMF) orientations to determine these locations, we adopt an analytical model based on previously derived formulations for magnetospheric and magnetosheath magnetic fields. The magnetospheric magnetic field is confined within a paraboloid. The magnetosheath magnetic field is derived from that in the solar wind and lies between the magnetopause and a paraboloid bow shock. We allow a slight diffusion of the magnetosheath magnetic field into the magnetosphere We compare the results of our model with previous predictions of the "component" and "antiparallel" merging models.

Concerning the occurrence pattern of flux transfer events on the dayside magnetopause

“…Cowley (1976) has shown that the reconnection lines (and therefore event axes) may exhibit any orientation lying between those of the magnetosheath and magnetospheric magnetic fields. The literature is replete with suggestions concerning the precise orientation of the reconnection line(s) as a function of magnetospheric and magnetosheath magnetic fields: they may lie along the locus of points where magnetopause currents peak (Alexeev et al, 1998) or alternatively along the locus of points where magnetosheath and magnetospheric magnetic fields exhibit the greatest reconnecting components (Moore et al, 2002), along the locus of points that maximizes the Alfvén speed characterizing the reconnection outflow (Swisdak and Drake, 2007), or parallel to the magnetopause current vector (Sonnerup, 1974;Gonzales and Mozer, 1974). The various models share one prediction crucial to the present study, namely that the inclination of the reconnection line(s) with respect to the ecliptic increases as the shear between the arbitrary magnetosheath and fixed northward magnetospheric magnetic field orientations decreases.…”

“…While various theories (Alexeev et al, 1998;Moore et al, 2002) and simulations (Dorelli et al, 2007) predict reconnection on the dayside magnetopause during periods of northward interplanetary and/or magnetosheath magnetic field orientation, and the evidence for such reconnection is compelling (Phan et al, 1996;Anderson et al, 1997;Chandler et al, 1999;Fuselier et al, 2000;Chandler and Avanov, 2003;Trattner et al, 2004;Oieroset et al, 2008), it is less certain that re-reconnection prevents FTEs from being observed there during periods of northward IMF orientation. Simultaneous reconnection (re-reconnection) at multiple sites is precisely the mechanism invoked to explain true flux ropes with symmetric bipolar magnetic field signatures normal to the nominal magnetopause during periods of southward IMF orientation (e.g., Lee and Fu, 1985;Raeder, 2006).…”

Tracking transient events through geosynchronous orbit

“…The extent of the region on the magnetopause in which merging can be expected broadens in merging models driven by current layer instabilities but remains equatorial for all but the most northward IMF orientations [Alexeev et al, 1998]. In antiparallel merging models, merging moves off the equator during periods of ecliptic or northward IMF orientations [Crooker, 1979].…”

Magnetopause mapping to the ionosphere for northward IMF

“…4 from Alexeev et al (1998). The magnetosphere -solar wind interaction is strongly controlled by the IMF direction, and it is significantly different for northward and southward IMF.…”

“…Both parts of the IMF (b and B scr ) have been obtained by Alexeev et al (1998). Inside the magnetosphere the solution of the IMF penetration problem is a uniform magnetic field:…”